This invention relates generally to mechanical and natural draft liquid cooling towers of the crossflow and counterflow types and more particularly to an improved inlet air control assembly for such towers.
In general, liquid cooling towers have a shell or enclosure defining a fill area in which is supported fill strips of various configurations. Liquid to be cooled descends through the fill area whereupon it is cooled by evaporation from the surface of droplets and films and by sensible heat transfer from water surfaces to air which is circulated through the fill area. The air is circulated into the tower through an air inlet and then through the fill area and exits through an air outlet. The air is forced into the air inlet by either mechanical means, such as fans, or by creating a natural draft by use of a natural draft chimney. In either case, the air enters between louver blades which are associated with the air inlet and exits through some form of stack or chimney associated with the air outlet.
There are a number of factors which determine the degree of cooling of a cooling tower design; among them being the quantity and temperature of the entering air. Needless to say, the lower the temperature and the greater the quantity of the inlet air, the greater the cooling capacity of the tower. Accordingly, it is common practice to design cooling towers which have the required capacity under conditions normally encountered during the hot summer months. That is, the air flow through the tower is designed such that a sufficient quantity of the hot summer air is drawn through the fill area to cool the liquid to the desired temperature. However, it has been found that when such towers are operated under cold winter conditions, the cold entering air causes the liquid adjacent to the air inlet to freeze on the louver blades, fill, and other support structures. The ice loads so created can be so large as to cause failure of the tower elements.
In such instances it is necessary to reduce the quantity of air which enters the tower through the air inlet. In the case of mechanical draft towers the fans can be either slowed down or shut off. However, in the case of natural draft towers there is no means to reduce the quantity of air which enters the tower. It has heretofore been proposed to install permanent wood panel members across some of the air inlet louver blades during the winter months to reduce the air flow into the tower. Although such wood panel members have been somewhat effective, it has been found the necessity to install and remove them each season is quite burdensome.